1. Field of the Invention
The present invention relates to an optical system and a stereoscopic image photographing apparatus having the optical system, which are adapted to obtain a stereoscopic image by leading images having parallax for right and left eyes (parallactical images) alternately in a time-series manner to one image sensor with a shutter means.
2. Description of Related Art
In order to observe a stereoscopic image, it is necessary to produce a plurality of parallactical images. Heretofore, there have been proposed a variety of stereoscopic-image-photographing optical apparatuses or stereoscopic-image-photographing optical systems for obtaining a plurality of parallactical images.
Among the above stereoscopic-image-photographing optical apparatuses or optical systems, there has been proposed, for example, in Japanese Laid-Open Patent Application No. Hei 6-327036, a stereoscopic image photographing apparatus in which images having parallax for right and left eyes are led alternately in a time-series manner to one and the same area of one image sensor by utilizing a liquid crystal shutter. Referring to FIG. 1 set forth in Japanese Laid-Open Patent Application No. Hei 6-327036, the stereoscopic image photographing apparatus is composed of two reflection mirrors provided respectively for right and left eyes, a liquid crystal shutter arranged to be drivable divisionally in area, and a photographic lens. Then, the liquid crystal shutter is disposed in the vicinity of the entrance pupil of the photographic lens on the object side of the photographic lens, so that images having parallax for right and left eyes can be inputted alternately to one image sensor.
However, in Japanese Laid-Open Patent Application No. Hei 6-327036, there is no disclosure as to a zoom lens adapted for photographing a stereoscopic image, and, further, there is no disclosure as to a particular method of compensating for the shift of an image plane relative to a change of the object distance.
In an optical system for use in photographing a stereoscopic image, it is important to obtain parallactical images for right and left eyes with high optical performance, so as to enable a stereoscopic image to be observed well.
It is an object of the invention to provide an optical system and a stereoscopic image photographing apparatus which are capable of making it easy to manually or automatically adjust focus according to a change of the object distance and are capable of obtaining parallactical images excellent in optical performance.
To attain the above object, in accordance with an aspect of the invention, there is provided an optical system, which comprises a pair of front optical components, an optical member for superposing respective optical axes of the pair of front optical components on each other, a rear optical component disposed such that the superimposed optical axes coincide with an optical axis of the rear optical component, the rear optical component including a lens unit arranged to move during zooming, and a lens unit arranged to move during focusing and disposed on an object side of the lens unit arranged to move during zooming, and shutter means capable of independently controlling amounts of transmission of light fluxes respectively entering the pair of front optical components from an object, wherein the optical system forms parallactical images in a time-series manner by causing the shutter means to alternately change the amounts of transmission of light fluxes respectively entering the pair of front optical components from the object.
In addition, in accordance with another aspect of the invention, there is provided an optical system, which comprises a pair of front optical components, each of the pair of front optical components having an optical power, an optical member for superposing respective optical axes of the pair of front optical components on each other, a rear optical component disposed such that the superimposed optical axes coincide with an optical axis of the rear optical component, the rear optical component including, on a most object side thereof, a lens unit arranged to move during focusing, and shutter means capable of independently controlling amounts of transmission of light fluxes respectively entering the pair of front optical components from an object, wherein the optical system forms parallactical images in a time-series manner by causing the shutter means to alternately change the amounts of transmission of light fluxes respectively entering the pair of front optical components from the object.
In addition, in accordance with a further aspect of the invention, there is provided an optical system, which comprises, in order from an object side to an image side, a first lens unit of negative optical power, a second lens unit, the second lens unit moving during focusing, a third lens unit of positive optical power, the third lens unit moving during zooming, and a fourth lens unit of positive optical power, the fourth lens unit moving during zooming.
In addition, in accordance with a still further aspect of the invention, there is provided a stereoscopic image photographing apparatus, which comprises an optical system according to each of the above aspects, and an image sensor disposed on an image forming plane of the optical system.